Antifouling paint

ABSTRACT

The invention relates to an antifouling paint having a binder comprising a rosin material and an auxiliary film-forming resin, the paint including an ingredient having marine biocide properties, wherein the binder comprises a blend of the rosin material and an auxiliary film-forming resin in a ratio of 20:80 to 95:5 by weight, the auxiliary film-forming resin comprising 20-100% by weight of an acid-functional film-forming polymer (A) whose acid groups are blocked by groups capable of hydrolyzing or dissociating to leave a polymer soluble in sea water, the blocking groups being selected from divalent metal atoms bonded to a monovalent organic residue, divalent metal atoms bonded to a hydroxyl residue and monoamine groups which form an organic solvent soluble amine salt of the polymer, and 80-0% by weight of a non-hydrolyzing water-insoluble film-forming polymer (B).

This application is the national phase of International PatentApplication No. PCT/EP00/00398, filed on Jan. 18, 2000, and which claimspriority of European Patent Application No. 99300378.9, filed Jan. 20,1999.

This invention relates to antifouling paint. An antifouling paint isused as a top coat on ships' hulls to inhibit the settlement and growthof marine organisms such as barnacles and algae, generally by release ofa biocide for the marine organisms.

BACKGROUND OF THE INVENTION

Traditionally, antifouling paints have comprised a relatively inertbinder with a biocidal pigment which is leached from the paint. Amongthe binders which have been used are vinyl resins and rosin. The vinylresins are seawater-insoluble and paints based on them use a highpigment concentration so that there is contact between pigment particlesto ensure leaching. Rosin is a hard brittle resin which is very slightlysoluble in seawater. Rosin-based antifouling paints have been referredto as soluble matrix or eroding paints. The biocidal pigment is verygradually leached out of the matrix of rosin binder in use, leaving askeletal matrix of rosin which becomes washed off the hull surface toallow leaching of the biocidal pigment from deep within the paint film.

Many successful antifouling paints in recent years have been“self-polishing copolymer” paints based on a polymeric binder to whichbiocidal tri-organotin moieties are chemically bound and from which thebiocidal moieties are gradually hydrolyzed by seawater, as described forexample in GB-A-1457590. Self-polishing copolymer paints which releasenon-biocidal moieties are described in EP-A-69559, EP-A-204456,EP-A-529693, EP-A-779304, WO-A-91/14743, WO-A-91/09915, GB-A-231070 andJP-A-9-286933.

U.S. Pat. No. 4,675,051 describes a marine antifouling paint which isgradually dissolved in seawater and which comprises a binder which is aresin produced by the reaction of rosin and an aliphatic polyaminecontaining at least one primary or secondary amine group. EP-A-802243describes a coating composition comprising a rosin compound, a polymercontaining organisilyl ester groups and an antifoulant.

Rosin is not a very good film-former, and it is known to add otherfilm-forming resins to rosin based antifouling paints. This hassometimes led to paints which were difficult to wash off the hullsurface. The present invention seeks to improve rosin-based antifoulingpaints with respect to the strength of the paint film and/or thereliable eroding away of the rosin-based paint matrix after biocide hasbeen leached from the paint.

SUMMARY OF THE INVENTION

An antifouling paint according to the present invention has a bindercomprising a rosin material and an auxiliary film-forming resin, thepaint including an ingredient having marine biocide properties,characterized in that the binder comprises a blend of the rosin materialand an auxiliary film-forming resin in a ratio of 20:80 to 95:5 byweight, the auxiliary film-forming resin comprising 20-100% by weight ofan acid-functional film-forming polymer (A) whose acid groups areblocked by groups capable of hydrolyzing or dissociating to leave apolymer soluble in sea water, the blocking groups being selected fromdivalent metal atoms bonded to a monovalent organic residue, divalentmetal atoms bonded to a hydroxyl residue and monoamine groups which forman organic solvent soluble amine salt of the polymer, and 80-0% byweight of a non-hydrolyzing water-insoluble film-forming polymer (B).

DETAILED DESCRIPTION OF THE INVENTION

The rosin material is preferably rosin, particularly wood rosin oralternatively tall rosin or gum rosin. The main chemical constituent ofrosin is abietic acid. The rosin can be any of the grades soldcommercially, preferably that sold as WW (water white) rosin. The rosinmaterial can alternatively be a rosin derivative, for example amaleinised or fumarised rosin, hydrogenated rosin, formylated rosin orpolymerised rosin, or a rosin metal salt such as calcium, magnesium,copper or zinc rosinate.

The film-forming polymer (A) capable of hydrolyzing or dissociating to apolymer soluble in sea water is most preferably a hydrolysable polymerhaving at least one side chain bearing at least one terminal group ofthe formula:

wherein X represents

M is a metal selected from zinc, copper and tellurium; x is an integerof 1 to 2; R represents an organic residue selected from

and R1 is a monovalent organic residue, as described in EP-A-204456.

Such a hydrolysable polymer is preferably an acrylic polymer in which Xrepresents

M is copper and R represents

The parent acrylic polymer having a —COOH group in place of—X—[O—M—R]_(x) preferably has an acid value of 25-350 mg KOH/g. Mostpreferably the hydrolysable polymer has a copper content of 0.3-20% byweight and R¹ is the residue of a high boiling organic monobasic acid.Such hydrolysable polymers can be prepared by the processes ofEP-A-204456 and EP-A-342276. The copper-containing film-forming polymer(A) is preferably a copolymer comprising an acrylic or methacrylic esterwhose alcohol residue includes a bulky hydrocarbon radical or a softsegment, for example a branched alkyl ester having 4 or more carbonatoms or a cycloalkyl ester having 6 or more atoms, a polyalkyleneglycol monoacrylate or monomethacrylate optionally having a terminalalkyl ether group or an adduct of 2-hydroxyethyl acrylate ormethacrylate with caprolactone, as described in EP-A-779304.

The hydrolysable film-forming polymer (A) can alternatively be acarboxylic acid-functional polymer, for example a copolymer of acrylicor methacrylic acid with one or more alkyl acrylate or methacrylate, atleast some of the acid groups of which have been converted to groups ofthe formula —COO—M—OH, where M is a divalent metal such as copper, zinc,calcium, magnesium or iron, as described in GB-A-2311070.

The film-forming polymer (A) can alternatively be a salt of an amine,preferably an amine containing at least one aliphatic hydrocarbon grouphaving 8 to 25 carbon atoms and an acid-functional film-forming polymeras described in EP-A-529693. The acid-functional polymer is preferablyan addition copolymer of an olefinically unsaturated carboxylic acid,sulphonic acid, acid sulphate ester, phosphonic acid or acid phosphateester and at least one olefinically unsaturated co-monomer. Theunsaturated carboxylic acid can for example be acrylic or methacrylicacid. The unsaturated sulphonic acid can for example be2-acrylamido-2-methylpropane sulphonic acid (AMPS), for example thefilm-forming polymer (A) may preferably be an amine sulphonate copolymercontaining units of an organocyclic ester as described in our co-pendingapplication GB 9801747.8.

The non-hydrolyzing water-insoluble film-forming polymer (B) can forexample be a vinyl ether polymer, for example a poly(vinyl alkyl ether)or a copolymer of a vinyl alkyl ether with vinyl acetate or vinylchloride, an acrylate ester polymer such as a homopolymer or copolymerof one or more alkyl acrylates or methacrylates which preferably contain1 to 6 carbon atoms in the alkyl group and may contain a co-monomer suchas acrylonitrile or styrene, or a vinyl acetate polymer such aspolyvinyl acetate or a vinyl acetate vinyl chloride copolymer. Thepolymer (B) can alternatively be a polyamine, particularly a polyamidehaving a plasticising effect such as a polyamide of a fatty acid dimeror the polyamide sold under the Trademark “Santiciser”.

We have found that the paints of the invention have the optimumcombination of film-forming and eroding properties when thenon-hydrolyzing water-insoluble film-forming polymer (B) is present inthe composition, albeit as a minor proportion of the auxiliaryfilm-forming resin. Most preferably the weight ratio of rosin to totalauxiliary film-forming resin is from 25:75, 50:50 or 55:45 up to 80:20.The hydrolyzing or dissociating film-forming polymer (A) preferablyforms at least 30, most preferably at least 50, up to 80 or 90% byweight of the auxiliary film-forming resin, the non-hydrolyzingwater-insoluble polymer (B) being the remainder.

The antifouling paint can include a non-polymeric plasticiser. Such aplasticiser can for example be present at up to 50% by weight based onthe total binder polymer, most preferably at least 10% and up to 35% byweight based on binder polymer. Examples of such plasticisers arephthalate esters such as dibutyl phthalate, butyl benzyl phthalate ordioctyl phthalate, phosphate triesters such as tricresyl ortris(isopropyl)phenyl phosphate, or chlorinated paraffins.

The rosin and the polymers forming the auxiliary film-forming resin canbe mixed in a common solvent which forms at least part of the paintsolvent, for example an aromatic hydrocarbon such as xylene, toluene ortrimethylbenzene, an alcohol such as n-butanol, an ether alcohol such asbutoxyethanol or methoxypropanol, an ester such as butyl acetate orisoamyl acetate, an ether-ester such as ethoxyethyl acetate ormethoxypropyl acetate, a ketone such as methyl isobutyl ketone or methylisoamyl ketone, an aliphatic hydrocarbon such as white spirit, or amixture of two or more of these solvents. The paint can alternatively bewater-based, for example it can be based on a commercial aqueous rosindispersion.

The binder may be the ingredient having marine biocide properties (forexample some long chain amines used to form amine salt copolymers arebiocidal) but more usually the binder is mixed with a biocide foraquatic organisms and usually with a pigment using conventionalpaint-blending techniques. The biocide may itself be all or part of thepigment of the paint. The coating composition preferably has a pigmentvolume concentration of, for example, 15 to 55%. The pigment preferablycomprises at least one sparingly soluble metalliferous pigment having asolubility in seawater of from 0.5 to 10 parts per million by weight.Examples of such pigments which are also aquatic biocides include copperor zinc compounds, such as cuprous oxide, cuprous thiocyanate, cuproussulphate, zinc ethylene bis(dithiocarbamate), zinc dimethyldithiocarbamate, zinc pyrithione, copper pyrithione, zinc diethyldithiocarbamate, copper resinate or cuprous ethylenebis(dithiocarbamate). Other sparingly soluble pigments having asolubility in sea water of 0.5 to 10 parts per million include bariumsulphate, calcium sulphate, dolomite and zinc oxide. Mixtures ofsparingly soluble pigments can be used, for example cuprous oxide,cuprous thiocyanate or zinc ethylene bis(dithiocarbamate), which arehighly effective biocidal pigments, can be mixed with zinc oxide, whichis not effective as a biocide but dissolves slightly more rapidly inseawater. Copper metal can be present as an aquatic biocide, for examplein flake or powder form.

The antifouling coating composition can contain a non-metalliferousbiocide for marine organisms, for example tetramethyl thiuramdisulphide, methylene bis(thiocyanate), captan,pyridiniumtriphenylboron, a substituted isothiazolone such as4,5-dichloro-2-n-octyl-4-isothiazolin-3-one,2-methylthio-4-t.butylamino-6-cyclopropylamino-s-triazine,N-3,4-dichlorophenyl-N′,N′-dimethyl-urea (“Diuron”),2-(thio-cyanomethylthio) benzothiazole,2,4,5,6-tetrachloro-isophthalonitrile, dichlorofluanid, tolylfluanid or2,3,5,6-tetrachloro-4-(methyl-sulphonyl)pyridine. Such anon-metalliferous biocide can be used as the only biocide of the coatingin a copper-free, or even metal-free or pigment-free, antifoulingcoating. Many of these non-metalliferous biocides are solid and all aresparingly soluble in seawater and may help the “self-polishing” actionof the paint.

The coating composition can additionally contain a pigment which is notreactive with seawater and may be highly insoluble in seawater(solubility below 0.5 part per million by weight) such as titaniumdioxide or ferric oxide or an organic pigment such as phthalocyanine orazo pigment. Such highly insoluble pigments are preferably used at lessthan 60% by weight of the total to pigment component of the paint, mostpreferably less than 40%. The coating composition can additionallycontain conventional thickeners, particularly thixotropes such as silicaor bentonite and/or stabilisers, for example zeolites or aliphatic oraromatic amines such as dehydroabietylamine.

The invention is illustrated by the following Examples:

EXAMPLES 1 TO 14

The following materials were mixed in the stated % by weight in a highspeed disperser to form antifouling paints according to the invention.

Example No.: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Rosin 10.01 10.01 10.09 9.68 10.06 10.00  9.94  9.93 10.01  7.81  4.27  9.83 11.08  3.88Hydrolysable acrylic Polymer (A1)  4.89 — —  6.66  5.54 —  5.47  5.46 5.51  9.42 12.07 — — — Hydrolysable acrylic Polymer (A2) —  5.37  5.56— — — — — — — —  6.09  6.86 11.98 Hydrolysable acrylic Polymer (A3) — —— — —  4.37 — — — — — — — — Non-hydrolyzing acrylic polymer (B1)  1.72 1.30 — — — —  1.18  1.18  1.19  2.03  2.50  0.58  0.65  1.14Non-hydrolyzing acrylic polymer (B2) — — 1.11 —  1.11  1.10 — — — — — —— — Tris(isopropylphenyl)phosphate  5.11  5.11  5.15  4.95  5.14  5.11 5.08  5.07  5.11  2.13  2.03 — —  4.08 plasticiser Red copper oxide37.58 37.55 37.87 36.34 37.83 37.59 37.38 37.33 37.65 36.04 34.24 — — —Purple copper oxide — — — — — — — — — — — 38.70 39.56 36.06 Zinc Oxide11.92 11.91 12.01 11.52 11.96 11.88 11.81 11.80 11.92 11.39 10.82 12.2512.52 11.41 Zinc ethylene bis(dithiocarbamate)  2.88  2.88 — — —  4.10 — 4.08 —  1.97 — — — — Zinc pyrithione — —  1.94  1.86 — — — — — — — — —— Copper pyrithione — — — — — —  3.95 — — —  3.62 — — — Organic biocide(C1)  0.76  0.76  1.28  1.23 — — — — — — — — — — Organic biocide (C2) —— — —  2.39 — — — — — — — — — Dichlorofluanid — — — — — — — —  3.46 1.66 —  2.95  3.02  2.75 Synthetic iron oxide  2.81  2.81  2.59  6.18 4.10  4.07 — — — — — — — — Natural iron oxide — — — — — —  3.56  3.56 3.59  3.43  3.71 — — — Carbon black — — — — — — — — — — —  0.99  1.02 0.93 Solvent 19.61 19.61 19.69 20.59 19.66 19.57 19.43 19.4  19.3422.00 24.72 18.71 19.5  25.74 Additives  2.70  2.70  2.60  0.98  2.23 2.22  2.20  2.20  2.22  2.12  2.02  2.18  2.23  2.03

Acrylic polymer A1 is an acrylic acid copolymer substantially accordingto Production Example 1 of EP-A-779304 in which the acrylic acid unitsare blocked by copper atoms bound to naphthenic acid residues.

Acrylic polymer A2 is similar to A1 but is based on an acrylic acidcopolymer having a higher content of methoxypolyethylene glycolmethacrylate.

Acrylic polymer A3 is a copolymer of the methyl bis (hydrogenatedtallow) amine salt of 2-acrylamido-2-methylpropanesulphonic acid,isobornyl methacrylate and isobornyl acrylate in mole ratio27.5:47.5:25.

Acrylic polymer B1 is an alkyl acrylate ester polymer sold under theTrademark “Paraloid B66”. Acrylic polymer B2 is a n-butyl acrylatepolymer sold under the Trademark “Acronal 4F”. Organic biocide C1 is4,5-dichloro-2-n-octyl-4-isothiazoline-3-one. Organic biocide C2 is soldunder the Trademark “Irgarol 1051”.

The solvent comprised mainly xylene with minor amounts of methyl isoamylketone, methyl isobutyl ketone and n-butanol. The rosin and acrylicpolymers were dissolved in solvent before being mixed with the otherpaint ingredients.

Additives comprised an organo-clay structuring agent, silica, carbonblack and molecular sieve zeolite.

As a test of antifouling performance the paints of Examples 1-14 wereeach applied to plywood boards which had been pre-painted with acommercial anti-corrosive primer and the boards were immersed in the seaat Newton Ferrers, Devon, England, Burnham-on-Crouch, Essex, England andSingapore. As a comparative test, primed boards were coated with a rosinpaint having a formulation similar to Example 1 but containing extra“Paraloid B66” in place of the hydrolysable acrylic polymer. Theseboards were immersed at the same time and at the same sites ascomparisons to both Examples 1 and 2; the paints of Examples 3 to 14were immersed similarly but not in a comparative experiment. The paintfilms were periodically assessed for settlement of marine foulingorganisms and the results are shown below.

In all results quoted below, 100=Totally clean, 0=Totally fouled.

Example Average fouling rating number of sites 1 76.4 6 Comparative 170.6 6 2 71.3 3 Comparative 2 59.0 3 3 84.2 3 4 83.3 3 5 87.0 2 6 76.3 67 86.5 4 8 88.0 4 9 88.0 4 10 — — 11 — — 12 84.3 3 13 84.0 1 14 89.3 3

What is claimed is:
 1. An antifouling paint having a binder comprising arosin material and an auxiliary film-forming resin, the paint includingan ingredient having marine biocide properties, wherein the bindercomprises a blend of the rosin material and an auxiliary film-formingresin in a ratio of 20:80 to 95:5 by weight, the auxiliary film-formingresin comprising 20-100% by weight of an acid-functional film-formingpolymer (A) whose acid groups are blocked by groups capable ofhydrolyzing or dissociating to leave a polymer soluble in sea water, theblocking groups being selected from divalent metal atoms bonded to amonovalent organic residue, divalent metal atoms bonded to a hydroxylresidue and monoamine groups which form an organic solvent soluble aminesalt of the polymer, and 80-0% by weight of a non-hydrolyzingwater-insoluble film-forming polymer (B).
 2. An antifouling paintaccording to claim 1 wherein the rosin material is rosin.
 3. Anantifouling paint according to claim 1 wherein the binder comprises ablend of the rosin material and the auxiliary film-forming resin in aratio of 55:45 to 80:20 by weight.
 4. An antifouling paint according toclaim 1 wherein the auxiliary film-forming resin comprises 30-90% byweight of the film-forming polymer (A) capable of hydrolyzing ordissociating to a polymer soluble in sea water and 70-10% by weight ofthe non-hydrolyzing water-insoluble film-forming polymer (B).
 5. Anantifouling paint according to claim 1 wherein the film-forming polymer(A) is a hydrolysable polymer having at least one side chain bearing atleast one terminal group of the formula:

wherein X represents

M is a metal selected from zinc, copper and tellurium; x is an integerof 1 to 2; R represents an organic residue selected from

and R1 is a monovalent organic residue.
 6. An antifouling paintaccording to claim 5 wherein the hydrolysable polymer is an acrylicpolymer in which X represents

M is copper and R represents


7. An antifouling paint according to claim 1 wherein the film-formingpolymer (A) is a carboxylic acid-functional polymer, at least some ofthe acid groups of which have been converted to groups of the formula—COO—M—OH, where M is a divalent metal.
 8. An antifouling paintaccording to claim 1 wherein the film-forming polymer (A) is a salt ofan amine and an addition copolymer of an olefinically unsaturatedsulphonic acid or acid sulphate ester and at least one olefinicallyunsaturated co-monomer.
 9. An antifouling paint according to claim 1wherein the film-forming polymer (A) is a salt of an amine and anaddition copolymer of an olefinically unsaturated carboxylic acid and atleast one olefinically unsaturated co-monomer.
 10. An antifouling paintaccording to claim 7 wherein the amine contains at least one aliphatichydrocarbon group having 8 to 25 carbon atoms.
 11. An antifouling paintaccording to claim 1 wherein the non-hydrolyzing water-insolublefilm-forming polymer (B) is an acrylate ester polymer or a vinyl etherpolymer.
 12. An antifouling paint according to claim 1 wherein thebinder includes a non-polymeric plasticiser present at up to 50% byweight based on the total binder polymer.
 13. An antifouling paintaccording to claim 8 wherein the amine contains at least one aliphatichydrocarbon group having 8 to 25 carbon atoms.
 14. An antifouling paintaccording to claim 2 wherein the binder comprises a blend of the rosinmaterial and the auxiliary film-forming resin in a ration of 55:45 to80:20 by weight.
 15. An antifouling paint according to claim 2 whereinthe non-hydrolyzing water-insoluble film-forming polymer (B) is anacrylate ester polymer or a vinyl ether polymer.
 16. An antifoulingpaint according to claim 3 wherein the non-hydrolyzing water-insolublefilm-forming polymer (B) is an acrylate ester polymer or a vinyl etherpolymer.
 17. An antifouling paint according to claim 4 wherein thenon-hydrolyzing water-insoluble film-forming polymer (B) is an acrylateester polymer or a vinyl ether polymer.
 18. An antifouling paintaccording to claim 5 wherein the non-hydrolyzing water-insolublefilm-forming polymer (B) is an acrylate ester polymer or a vinyl etherpolymer.
 19. An antifouling paint according to claim 6 wherein thenon-hydrolyzing water-insoluble film-forming polymer (B) is an acrylateester polymer or a vinyl ether polymer.
 20. An antifouling paintaccording to claim 7 wherein the non-hydrolyzing water-insolublefilm-forming polymer (B) is an acrylate ester polymer or a vinyl etherpolymer.
 21. An antifouling paint according to claim 8 wherein thenon-hydrolyzing water-insoluble film-forming polymer (B) is an acrylateester polymer or a vinyl ether polymer.
 22. An antifouling paintaccording to claim 9 wherein the non-hydrolyzing water-insolublefilm-forming polymer (B) is an acrylate ester polymer or a vinyl etherpolymer.
 23. An antifouling paint according to claim 13 wherein thenon-hydrolyzing water-insoluble film-forming polymer (B) is an acrylateester polymer or a vinyl ether polymer.
 24. An antifouling paintaccording to claim 14 wherein the non-hydrolyzing water-insolublefilm-forming polymer (B) is an acrylate ester polymer or a vinyl etherpolymer.